Fuse plug



G. R. BROWN FUSE PLUG Filed Dec. 9, 1931 H is Attorney Patented Oct. 3, 1933 1,929,272 4 UNITED STATES PATENT OFFICE FUSE PLUG George R. Brown, Bridgeport, Com, assignor to General Electric Company, a corporation of New York Application December 9, 1931. Serial No. 579,849 2 Claims. (Cl. 200130) My invention relates to electrical safety dethe same time provide means for keying the top vices and more particularly to fuse plugs. 11 to the base 12, a substantially cylindrical cen- In the manufacture of fuse plugs considerable tral chamber 16 is provided in the top having a difliculty has been experienced in finding a satfiat side 17 which is better indicated in Fig. 4.

isfactory means of keying the base, shell and top The top is provided with a magnifying lens in the 60 together so that the turning of the plug during its window to magnify the break in the fusible eleinsertion or removal from a receptacle will not ment located below this window. The outside of separate these parts and sever the fusible elethe top 11 is threaded to receive the shell 13 and ment which is connected between the center conhas a longitudinal groove 18 in which the fusible tact in the base and the shell. Also, it frequently element is adapted to rest. 65 happens that upon the blowing of a fuse such a Base 12 isof porcelain and has an extension high gas pressure is generated in the plug that 19 which is substantially cylindrical except for a the top of the plug will be shattered or separated flat side 20. This extension 19 is adapted to exfrom the other parts of the-plug. When the top tend within the chamber 16 of top 11 with the 15 of the plug becomes separated from the remainflat side 20 in engagement with the flat side 1'7 70 der of the plug as it is being removed from a rewithin the chamber to key the top 11 and base 12 ceptacle considerable difiiculty may be experitogether to prevent relative rotary movement beenced in removing the shell and base of the plug. tween the parts. The base is provided with a The object of my invention is to provide an knob 21 which is substantially square and has 20 improved fuse plug which shall permit of ready sharp edges. An opening 22 extends through the 75 inspection of the fusible element at all times and knob 21 and into the central chamber surroundwhich shall have its component parts so keyed ed by the extension 19. Rivet 14 is adapted to together that the blowing of the fusible element be seated in the opening 22 and its inner end or the frequent insertion or removal of the plug expanded to engage a shoulder 23 within the cen- 25 from a receptacle will not -cause a separation of tral chamber. th parts, Shell 13 is provided with threads and is of the What I consider to be novel and my invention usual form with the exception that it is provided will be better understood by reference to the folwith an angular shoulder 24 whose inner diameter lowing specification and appended claims when is substantially the same as the diagonal across 30 considered in connection with the accompanying the edges of the knob 21 on the base 12. This as drawing. shoulder 24, as best indicated in Fig. 3, is pressed In the drawing, Fig. 1 is a vertical section-of down so that it is flattened, except for the porthe plug; Fig. 2 is an exploded View of the plug tions which engage the sharp edges of knob 21, shown in perspective from the rear with the top to key the shell 13 to the base 12. Fusible element in section; Fig. 3 is a detail view of the rear of 15 is connected at one end to the inner side of 90 the plug in perspective; and Fig. 4 is a perspeccenter contact 14 by solder 25 as indicated in Fig. tive view of a section of the top of the plug at 1 and is then bent with a portion, including the right angles to its position in Fig. 2. reduced portion, parallel to the lens window,

In the drawing the fuse plug is indicated genacross the edge of top 11, and extends into the erally by the numeral 10 and comprises a top 11, recess 18 on the outside of top. The other end 95 a base 12 and a shell 13. A center contact 14 is of the fusible element 15 is connected to the shell mounted in the base and a fusible element 15 is by being soldered thereto. connected at one end to the center contact 14 In assembly of the fuse plug 10, the center conand at the other end to shell 13. The top 11 is tact 14 is first placed in position in the base 12 of a transparent material, preferably a glass. and its inner end expanded against the shoulder 100 having a high fusion point and low coeflicient of 23. One end of the fusible element 15 is soldered expansion, such as Pyrex. which will withstand to the center contact 14 and bent to the desired high gas pressures within the fuse plug and will shape. Base 12 is then inserted in the top 11 with not be easily broken by mechanical strain. The the extension 19 extending within the chamber use of such a glass for the top 11 presents difii- .5 and the flat side 20 in engagement with the 105 culties in the molding of the top because it is flat side 17 of chamber 16. Shell 13 is then practically impossible to mold narrow recesses threaded over the outside of top 11 until its end because of the high temperature of the molten abuts the end of base 12. The angular shoulder glass, which tends to burn any projecting portion 24 is then pressed flat with portions engaging the of the mold. To overcome this difficulty and at edges of the knob 21 asbest indicated in Fig. 3. no

The other end of the fusible element 15 is connected to the shell 13 by soldering or any other means desired. The fuse plug 10 is then completely assembled and ready for use.

From the foregoing it may be seen that a fuse plug is provided with a top of material which will withstand high gas pressures which'are frequently generated on the blowing of the fusible element and which is not likely to be damaged by mechanical strains. Also, the method of keying the base and top together is such as to reduce the likelihood of damage by mechanical strains or the blowing of the fuse. The keying of the shell to the base is positive and thus reduces to a minimum the likelihood that the shell should be separated from the remainder of the fuse plug or that there should be sufficient relative motion to sever the fusible element connected between the base and shell.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A fuse plug comprising a top of glass having a high fusion point threaded on the outside and having a central chamber substantially cylindrical with one fiat side extending a portion of its length, a base of insulating material with a substantially cylindrical portion at one end extending within the chamber of the top and having a flat side in engagement with the flat side of the chamber and a knob with sharp corners on the other end, a center contact secured in said base, a fusible element with one end connected to the center contact, and a metallic shell threaded on said top and having a shoulder engaging the sharp corners of said knob on the base and electrically connected to the other end of the fusible element.

2. A fuse plug comprising a top of glass having a high fusion point threaded on the outside and having a central chamber substantially cylindrical with one flat side extending a portion of its length and a longitudinal groove extending on the outside from the bottom to near the top, a base of insulating material with a substantially cylindrical portion at one end extending within the chamber of the top and having a flat side in engagement with the fiat side of the chamber and a square knob on the other end, a center contact secured in said base, a fusible element with one end connected to the center contact and seated in the groove of the top, and a metallic shell threaded on said top and having an angular shoulder engaging the corners of said knob and electrically connected to the other end of the fusible element.

GEORGE R. BROWN. 

